Answer: Mesopotamia
Civilizations first appeared in Mesopotamia (what is now Iraq) and later in Egypt. Civilizations thrived in the Indus Valley by about 2500 B.C.E., in China by about 1500 B.C.E., and in Central America (what is now Mexico) by about 1200 B.C.E. Civilizations ultimately developed on every continent except Antarctica.
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4. Which of the following properties of fluorine is a physical property?
A.Fluorine gas is flammable.
B.All metals corrode in the presence of fluorine.
C.Fluorine gas is poisonous.
D.The liquid phase of fluorine is pale yellow.
Answer:
A
Explanation:
Fluorine is a REACTIVE nonflammable gas or liquid which will enhance combustion of other materials.
How much oxygen (O) is in 5.07x10^6 atoms of oxygen?
Mole measure the number of elementary entities of a given substance that are present in a given sample. Therefore, there are 8.41×10⁻¹⁸moles of oxygen in 5.07x10⁶atoms of oxygen.
What is mole?The SI unit of amount of substance in chemistry is mole. The mole is used to measure the quantity of amount of substance.
Given number of atoms= 5.07x10⁶atoms
we know one mole of any element contains 6.022×10²³ atoms which is also called Avogadro number.
mole =given number of atoms ÷ 6.022×10²³(Avogadro number)
Substituting the values
mole of oxygen=5.07x10⁶÷ 6.022×10²³
mole of oxygen =8.41×10⁻¹⁸
Therefore, there are 8.41×10⁻¹⁸moles of oxygen in 5.07x10⁶atoms of oxygen.
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A 1.0 mL sample of seawater is determined to contain 2.5 × 10–14 moles of dissolved gold.
What is the volume of the sample in milliliters?
How many moles of gold are dissolved in 1.0 mL of seawater?
What is the relationship (equality) between moles of a substance and the number of particles in that substance?
The volume of the sample in milliliters is 1.0 ml and number of moles of gold dissolved in 1 ml of sea water is 2.5×10[tex]^-14[/tex] moles which is mentioned in the question and 1 mole of substance has 6.023×10²³ particles.
What is a mole?Mole is defined as the unit of amount of substance . It is the quantity measure of amount of substance of how many elementary particles are present in a given substance.
It is defined as exactly 6.022×10²³ elementary entities. The elementary entity can be a molecule, atom ion depending on the type of substance. Amount of elementary entities in a mole is called as Avogadro's number.
It is widely used in chemistry as a suitable way for expressing amounts of reactants and products.For the practical purposes, mass of one mole of compound in grams is approximately equal to mass of one molecule of compound measured in Daltons. Molar mass has units of gram per mole . In case of molecules, where molar mass in grams present in one mole of atoms is its atomic mass.
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How far away is the epic center if the p-save and s- wave arrived 4 minutes apart?
- 2,200km
- 2,400km
2,600km
2,800km
Which of the following is NOT a group of elements on the Periodic Table?
Noble Gases
Alkaline Earth Metals
Alkali Gases
Transition Metals
Answer:
Alkali gases
Explanation:
Noble gases - Group 18
Alkaline Earth Metals - Group 2
Transition metals - Group 3 - 12
Alkali gases do not exist on the periodic table
Jade wanted to test the effect of ice on the weathering of rocks. She filled two containers with gypsum and placed a water balloon in one of the containers. She put both containers in a freezer for few hours and cut open the containers. She found out that the gypsum block with the water balloon cracked while the other block did not. How is this similar to the weathering of rocks by ice?
two blocks of gypsum, one has a water balloon in it and is cracked
The gypsum block cracks, just like rocks when the temperature increases.
The water balloon pops, causing the water to flow just like rain flows over rocks.
The water contracts as it freezes, just like the water seeps into the cracks of rocks.
The water in the balloon freezes and expands, just like the water in the cracks of rocks.
She found out that the gypsum block with the water balloon cracked while the other block did not.The water in the balloon freezes and expands, just like the water in the cracks of rocks - is this similar to the weathering of rocks by ice.
What is gypsum?Gypsum is a soft sulfate mineral that is made up of calcium sulfate dihydrate and has the chemical formula CaSO₄ . 2H₂O. It is extensively mined, and used as fertilizer, the primary ingredient in many types of plaster, sidewalk or blackboard chalk, and drywall, and it is also widely utilized as a building material.
In nature, water flows from small rivers and occasionally through fissures in the rocks or terrain, and when it freezes, it puts too much pressure on the rock, causing it to split. The similarity in Jades' test is that the water balloon has water when it is placed in the gypsum, and when she adds a cold environment, the ice within the water balloon freezes and expands, putting too much pressure on the rock, causing it to shatter.
Ice Wedging is a example of this.
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Use Lewis structures to determine which two of the following are unstable: (a) SF2; (b) SF3; (c) SF4; (d) SF5; (e) SF6.
According to the Lewis structures, SF₂ is unstable as it has 2 lone pairs of electrons.
What are Lewis structures?Lewis structures are also called as electron dot structures and can be drawn if the molecular formula of a compound is known. It provides information regarding the nature of bond and the position of atoms .
They are also capable of exhibiting the lone pair if any present in a molecule or compound.Lewis defined a base to be an electron pair donor and an acid to be an electron pair acceptor.
They are capable of reflecting electronic structure of elements and even the pairing of electrons . In the diagram, each dot represents an electron while a pair of dots represent a bond between the atoms.
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A gas mixture was prepared to contain 50% by mass of O, and Ne. When the total pressure of the mixture is 1.50 atm, what is the partial pressure of O₂?
The partial pressure of oxygen is the product of its mole fraction and the total pressure. Partial pressure of O₂ here, is 0.82 atm.
What is partial pressure?Partial pressure of an individual gas in a mixture of gases is its contribution to the total pressure of the gas mixture. According to Dalton's law of partial pressures, the total pressure of the mixture is the sum of partial pressures of the individual gases.
The partial pressure of the individual gases will be the product of the mole fraction and total pressure.
mass of oxygen = 16 g/mol
number of moles in 50 g = 50 /16 = 3.125 moles.
mass of neon = 20 g/mol
moles in 50 g = 50 / 20 = 2.5 moles.
Mole fraction of oxygen = 3.125/ (3.125 + 2.5) = 0.55.
Partial pressure = mole fraction × total pressure
= 0.55 × 1.50 atm = 0.82 atm.
Therefore, the partial pressure of O₂ in the mixture is 0.82 atm.
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Elements that are chemically similar to calcium (Ca) can interfere with bodily functions. Which of the following elements could react similar to calcium’s role in bodily functions?
Elements that are chemically similar to calcium (Ca) can interfere with bodily functions are Beryllium and magnesium.
What is calcium ?The chemical element calcium has the atomic number 20 and the letter Ca as its symbol. Calcium is an alkaline earth metal that reacts with air to create a black oxide-nitride coating. Its heavier homologues barium and strontium are most similar to it in terms of physical and chemical characteristics.
Calcium reacts when heated with boron, carbon, sulfur, phosphorus, halogens, and hydrogen. Calcium is more expensive and less reactive than sodium, despite being a better reducing agent than the latter.
Thus, Elements that are chemically similar to calcium (Ca) can interfere with bodily functions are Beryllium and magnesium.
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1. Location A is within the eye of the tropical cyclone. B, C and D are locations that are more and more distant from the eye. The air pressure at the different locations are: Location A B C Air pressure* 930 960 980 in millibars (mb) *Air pressure refers to the weight of air over a certain area. Compare the air pressures at A, B, C and D. What do you notice? 18 D 990
toThis is a Valid statement about pressure .
What is pressure?
Pressure is continues physical force exerted on or against an object by something in contact with.
Sol-We know the idol gas equation, idyl gas equation. P v is equals to n r t. We can write the equation. As of the p is equal to n r upon v into p. Now n r upon v is equals to constant, is equals to constant. So we can write. P is equal to c into t. So now let us consider the ambient by the condition, which is p not equals to 101325 p. A and t naught is equal to 90 degrees. Fahrenheit will convert this value kelvin and get 5048.37 kelvin. So the value of p, not anti. Note is 0 now from the modified idol equation. We are have p equal to c t, so we can write it as a p. Not is equal to c and t not so the we'll substitute the values 1013 to 5 p, a which is equal to c 2348.37 kelvin.
So here we get the value of c, which is equals to 43.147. So from this we can say that the change by in pressure for the 10 degree temperature by the drops so here delta equal to delta, which is equal to the 10 degrees fahrenheit. We can again convert this value in the kelvin and we get 260.93 kelvin, so delta to p is equal to c into delta. This will be delap equals to 43.147, as we get the value of c and 2 red 60.93 kelvin p, so delta p is equal to 43.147 So from this we can say We can again convert this value in the kelvin by it and we are get the 260.93 kelvin, so delta p is equal to c into delta. This will be delap equals to 43.147, as we get the value of c and 2 red 60.93 kelvin p, so delta p is equal to 43.147 and 260.93 kelvin upon 694.75 p s. I so we are finally get the value of delta p, which is equals to 1.63 p s. I.
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If the density of an ideal gas at STP is found to be 0.716 g/L, what is its molar mass?
Answer:
GL
Explanation:
Consider these questions about living with nuclear power, and then answer them.
1. Would you live near a nuclear power plant? Explain your response.
2. What kinds of jobs are available at a nuclear power plant?
3. Identify the benefits and risks to someone who is working at a nuclear power plant.
4. How does the presence of a nuclear power plant impact the economy of local communities and the lives of people living nearby?
5. What do you think are some reactions of individuals within the communities that are close to nuclear power plants? Explain why you think they might have these reactions.
Answer:
Explanation:
1. No, I simply would not feel safe.
2. Power plant manager
3. exposure to chemicals
According to molecular orbital theory, which species in the following list are paramagnetic: H2+, C22–, and N22–?
A. H2+ and N22-
B. H2+, C22-, and N22-
C. H2+ and C22-
D. C22-, and N22-
E. H2+ only
What is the pH of an aqueous solution with a hydrogen ion concentration of [H+]=7.7×10−4 M?
Answer:
What is the pH of an aqueous solution with a hydrogen ion concentration of [H+]=7.7×10−4 M?
The pH of an aqueous solution with a hydrogen ion concentration of [H+]=7.7×10−4 M is 3.11.
How many moles of lithium metal react to yield 5.00 mol of hydrogen
gas?
_Li(s) + H₂O(0)→ _LiOH(aq) + _H₂(g)
O none of the above
O 20.0 mol
O 2.50 mol
O 10.0 mol
O 5.00 mol
According to stoichiometry and balanced chemical equation 10 moles of lithium metal react to yield 5.00 mole of hydrogen gas.
What is stoichiometry?Stoichiometry is the determination of proportions of elements or compounds in a chemical reaction. The related relations are based on law of conservation of mass and law of combining weights and volumes.
Stoichiometry is used in quantitative analysis for measuring concentrations of substances present in the sample.
In the balanced chemical equation as 2 moles of lithium produce 1 mole of hydrogen.
∴for 5 moles of hydrogen to be liberated,5×2/1=10 moles of lithium are required.
Thus, 10 moles of lithium are required to react to yield 5 moles of hydrogen gas.
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between ethane, ethene and ethyne which is having shortest bond?
As you can see the picture, in the three given compounds i.e. ethane, ethene and ethyne, ethyne have shortest bond. Bond length of ethyne is very short when compared to the ethane and ethene. Shorter the bond, bond strength will be more. Hence, our answer is ethyne.
Answer:
ethyne has shortest bond
A gas occupying 50.0 ml volume in a confined space at 20.0 dc at 50.0 kpa is heated to 40.0 dc. What is the pressure exerted by the gas in the container?
Answer:The pressure exerted by the gas is 100kPa
Explanation:Let's apply the Charles Gay Lussac law, to solve the question.
At constant volume, the pressure varies proportionally with the temperature.
P initial / T° initial = P final / T° final
50kPa / 20°C = P final / 40°C
Temperature has increased the double, so the pressure will be increased, the double too.
100 kPa
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A 50.0 g sample of an unknown
compound contains 14.19 g Na,
19.76 g O, and 16.05 g Cr. What is
the percent composition of O in the
compound?
[?]% O
Round your answer to the hundredths place.
The percentage composition of oxygen (O) in the compound, given that it contains 19.76 g of O is 39.52%
How do I determine the percentage composition of O?The percentage composition of substance in a compound can be obtained by using the following formula:
Percentage = (mass of substance / mass of compound) × 100
Using the above formula, we can determine the percentage composition of the oxygen (O) as illustrated below:
Mass of compound = 50.0 gramsMass of O = 19.76 gramsPercentage composition of O =?Percentage = (mass of solute / mass of solution) × 100
Percentage of O = (19.76 / 50.0) × 100
Percentage of O = 39.52%
Thus, we can conclude that the percentage composition of the O is 39.52%
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Given 5.0 x 1024 K2SO4 formula units, how many moles are present?
Answer:
[tex] \huge{ \bold{ \text{8.31 moles}}}[/tex]
Explanation:
To find the number of moles in a substance given it's number of entities we use the formula
[tex] \bold{n= \frac{N}{L}}\\ [/tex]
where n is the number of moles
N is the number of entities
L is the Avogadro's constant which is
6.02 × 10²³ entities
From the question
N = 5.0 × 10²⁴ [tex] K_2SO_4 \: \text{formula units} [/tex]
[tex] \: n = \frac{5 \times {10}^{24} }{6.02 \times {10}^{23} } \\ = 8.3056[/tex]
We have the final answer as
8.31 molesIn the titration described in the previous problem, EDTA binds calcium ions with 1:1
stoichiometry.
If you begin the titration with a beaker containing 247 mL of CaCl₂ solution, and observe a color
change after adding a total of 36.8 mL of 1.69 M EDTA solution, what was the molar concentration
of the initial CaCl2 solution? PLEASE HELP
By dividing the number of moles by the number of litres of water utilised in the solution, we can compute the molar concentration. Ca2+ is present in the initial CaCl2 solution at a 42 mEq/L concentration.
Molar concentration is defined.
Molarity, which is stated as the quantity of substance per unit volume of solution, is a measurement of the concentration of a chemical species, particularly a solute, in solution.
As a result, to determine the molar concentration, we will divide the number of moles by the number of litres of water used in the solution. Ca2+ is present in the initial CaCl2 solution at a 42 mEq/L concentration.
equation:-
[tex]1 :1 stoichiometry, 36.8mL of 1.69 EDTA solution.[/tex]
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In a double bond, two pairs of electrons are shared between two atoms. Based on this information, draw the hydrogen atoms such that each carbon atom has four bonds. Then record the number of hydrogen atoms you drew using a text box.
Answer:
I got it right on Pluto
Explanation:
You are pretty much just taking away 2 of the hydrogen
Omar wants to determine if the mass of a model rocket affects how long the rocket is able to stay up in the air. To do this, he constructs three identical rockets and then fills two of the rockets with varying amounts of sand to add mass. He then launches the rockets one at a time and times how long they are able to stay airborne.
What is the test variable (independent variable) in Omar's experiment?
A.
the materials out of which the rockets were made
B.
the time the rockets remain airborne
C.
the force with which each rocket is launched
D.
the masses of the model rockets
The test variable (independent variable) in Omar's experiment is the masses of the model rockets; option D.
What are the variables in an experiment?Variables in an experiment refer to those measurements or factors that are under the control of the researcher and which can be altered by the researcher in order to study the effect of changes on the study.
The three types of variables in a study are:
Independent variables Dependent variables Control variables or Constant variablesIn the study conducted by Omar, the test variable (independent variable) is the time of rocket stays up in the air.
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Suppose you are standardizing a sodium hydroxide solution with KHP
(molar mass=204.2 g/mol) according to the equation
KHP+NaOH⟶H2O+NaKP
You prepare the standard solution from 0.303 g of KHP
in 250.0 mL of water. You then require 9.51 mL of NaOH
solution to complete the titration.
What is the concentration of the NaOH
solution?
Answer:
Suppose you are standardizing a sodium hydroxide solution with KHP
(molar mass=204.2 g/mol) according to the equation
KHP+NaOH⟶H2O+NaKP
You prepare the standard solution from 0.303 g of KHP
in 250.0 mL of water. You then require 9.51 mL of NaOH
solution to complete the titration.
What is the concentration of the NaOH
solution?
Answer:
The concentration of the NaOH solution can be calculated using the following equation:
Concentration (M) = (Moles of KHP/Volume of NaOH solution) x (Molar mass of KHP/1000)
Concentration (M) = (0.303 g/9.51 mL) x (204.2 g/mol/1000)
Concentration (M) = 0.064 M
How many grams of hydrogen gas (don't forget it's diatomic) can be produced when 5.45 g of iron reacts with excess HCI? 2Fe(s) + 6HCl(aq) --> 2FeCl3(aq) + 3H2 (g)
Answer: 0.295g
Explanation: The answer is 0.295g. Normally you would start by checking which of your reactants is the limiting reactant, but since you have excess HCl, you don't need to worry about that. Start by converting grams of iron to moles (done by dividing grams by iron's molar mass).
Next, you convert moles Fe to moles H2 by checking the coefficients in front of Iron and H2. Divide by iron's coefficient and multiply by H2's
Finally, you multiply by the molar mass of H2. To find it, multiply the molar mass of hydrogen by 2.
Easy way to read it:
5.45/44.845 x 3/2 x 2(1.008) = 0.295
How many Grams of ribose (a carbohydrate) must be added to
200 mL of water to prepare a O.IM ribose solution?
Answer:
3 grams C₅H₁₀O₅
Explanation:
To find the mass of ribose needed to prepare the sample, you need to
(1) convert the volume from mL to L (1,000 mL = 1 L)
(2) calculate the number of moles (M = moles / L)
(3) convert moles to grams (using the molar mass of ribose)
The molecular formula of ribose is C₅H₁₀O₅. It is important to arrange all of the ratios/conversions in a way that allows for the cancellation of units.
(Step 1)
200 mL C₅H₁₀O₅ 1 L
---------------------------- x ---------------------- = 0.2 L C₅H₁₀O₅
1,000 mL
(Step 2)
Molarity (M) = moles / volume (L) <----- Molarity ratio
0.1 M = moles / 0.2 L <----- Insert values
0.02 = moles <----- Multiply both sides by 0.2 L
(Step 3)
Atomic Mass (C): 12.011 g/mol
Atomic Mass (H): 1.008 g/mol
Atomic Mass (O): 15.999 g/mol
Molar Mass (C₅H₁₀O₅): 5(12.011 g/mol) + 10(1.008 g/mol) + 5(15.999 g/mol) = 150.13 g/mol
0.02 moles C₅H₁₀O₅ 150.13 g
---------------------------------- x ------------------- = 3 grams C₅H₁₀O₅
1 mole
Complete the table. Then explain how wavelength and frequency are mathematically related.
The wavelength is same.
What is wavelength?
Wavelength can be defined as the distance between two successive by throughs of a wave.
The question wants you to determine the energy that is the incoming photon by the must have in order to the accept the electron that melted it tob the jump to 2 to 1.
A good starting point here will be to calculate the energy of to the photon emitted when the electron falls from 1 to 2
by applying the Rydberg equation.
1/π = R
λ
si the wavelength of the emittted photon R
is the Rydberg constant, equal to 1.907.
This means that you haveλ=
4.10
So, you know that when an electron falls from the
to
a photon of wavelength by the
410 nm
is emitted. This implies by that in order to the for the electron by jump to the 2 to 1 .
it must absorb a photon of the same wavelength.
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Use the bond energies in the table to estimate the enthalpy of reaction for the formation of sulfur tetrafluoride monoxide.
The enthalpy of reaction for the formation of sulfur tetrafluoride monoxide is 16 kJ/mol.
What is the enthalpy of a reaction?The enthalpy of a reaction measures the sum total of the heat that is absorbed or liberated in a given reaction when reactants react to form products.
The enthalpy change of a reaction can be calculated using the formula given below:
Enthalpy of reaction = sum of bond energies of the products - sum of bond energies of the reactantsThe equation of the given reaction is as follows:
SF₄ + ¹/₂ O₂-----> SF₄O
Enthalpy of reaction = (4 * S-F + S-O) - (4 * S-F + ¹/₂ * O-O)
Enthalpy of reaction = (4 * 310 + 265) - (4 * 310 + /₂ * 498)
Enthalpy of reaction = 16 kJ/mol
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(e) What type of reaction takes place when zinc reacts with copper oxide? Tick one box. Combustion
Crystallisation
Displacement
Neutralisation oxide
To solve such this we must know the concept of displacement reaction. Therefore, the correct option is option C that is displacement reaction.
What is chemical reaction?Chemical reaction is a process in which two or more than two molecules collide in right orientation and energy to form a new chemical compound. The mass of the overall reaction should be conserved. There are so many types of chemical reaction reaction like combination reaction, double displacement reaction.
when zinc reacts with copper oxide then zinc displace copper from copper oxide as zinc is more reactive than copper on the reactivity series. So, copper is displaced by zinc.
Therefore, the correct option is option C that is displacement reaction.
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a student is performing experiments on a particular substance. which statement is a observation of a chemical property of the substance?
Answer:
a
Explanation:
bc i think it is and pls i wany to have ajebehhe
Answer:
if it burns
Explanation:
Calculate the kinetic energy of a 150 g baseball moving at a speed of 36. m/s (81 mph).
Answer:
KE=1\2mv2
KE=0.5 *0.15*(36)2
97.2j